1. Field of the invention
This invention relates to a linear guide device used for linear sliding in an industrial machine or the like, and particularly to improvements in ball circulating parts in the device.
2. Related Background Art
The appearances of a linear guide device in the prior art are shown in FIG. 15 of the accompanying drawings, and a cross-sectional view along the direction of line 16xe2x80x9416 of FIG. 15 showing the internal structure thereof is shown in FIG. 16 of the accompanying drawings. As shown, the linear guide device is comprised of a guide rail 50 having in the outer surface thereof a groove portion 57 receiving therein rolling members, i.e., balls 51 for rolling and extending axially, and a slider 60 having therein a circulation path 4 for the balls 51 and held for sliding on the guide rail 50 by the balls 51 in a groove portion 7 (see FIG. 11 of the accompanying drawings) opposed to the groove portion 57. The balls 51 are held in the circulation path 4 and between the two groove portions 57 and 7 and roll in the circulation path 4 and between the two groove portions 57 and 7 with the sliding movement of the slider 60. The slider 60 is comprised of a slider body 1 having the circulation path straight portion 5 of the ball circulation path 4 and an end cap 2 having a circulation path curved portion 6 communicated with the straight portion 5 and between the two groove portions 57 and 7 to thereby make the ball circulation path 4 into an endless track.
As the ball circulating parts in the linear guide device heretofore used, i.e., the slide body 1 and the end cap 2, mention may be made of ones disclosed in Japanese Patent Publication No. 62-11215 shown, for example, in FIGS. 11 and 12 of the accompanying drawings. FIG. 11 is a view of the joined surface in the slider body 1 with the end cap 2 as it is seen from the direction of joint, and FIG. 12 is a view of the joined surface in the end cap 2 with the slider body 1 as it is seen from the direction of joint.
The slider body 1 is formed with the straight portions 5 of the circulation path, and the grooves 7 for the balls 51 to support the slider 60 relative to the guide rail 50 and further, the opening portions of the straight portions 5 of the circulation path are formed with tapered surfaces 20 having their opening diameter enlarged toward the opening portions. In FIGS. 11 and 12, the reference numeral 21 designates mounting threaded holes for mounting the end cap 2 on the slider body 1, and the reference numeral 30 denotes chamfered portions for facilitating the rolling of the balls 51.
The end cap 2 is formed with the circulation path curved portions 6 which are semicylindrical holes relative to the vertical direction in the plane of the drawing sheet and are concave grooves having a semicircular cross-section along the circumferential surfaces of the semicylindrical holes and which communicate with the straight portions of the circulation path of the slide body and a ball holding portion formed between the groove portions 7 of the slider body and the groove portion 57 of the guide rail 50. The reference numeral 22 designates through-holes for passing therethrough screws for mounting the end cap 2 on the slider body 1, and the reference numeral 31 denotes a pickup portion for picking up the balls 51 into the circulation path curved portions 6.
The communicating portion in the circulation path curved portions 6 with the circulation path straight portions 5 of the slider body 1, as shown in FIG. 13 of the accompanying drawings which schematically shows the cross-section of the communicating portion (fitting portion), is formed with a substantially circular-ring-like protruding portion 25 formed with a taper fitted correspondingly to the tapered surfaces 20 in the circulation path straight portions 5, and the slider body and the end cap are designed to be faucet-fitted to each other in this communicating portion. Further, a tapered portion 26 increasing its opening diameter relative to the communicating portion is formed on the inner surface of the substantially circular-ring-like portion of the protruding portion 25 in the end cap 2 so that the smooth circulation of the balls may be obtained.
However, in the faucet-fitted portion as shown above, the fitted portion is formed by the tapered surfaces 20 of the slider body 1 and the protruding portion 25 of the end cap 2, and when an error of positional dimensions occurs to the fitted portion, it is difficult to absorb it by the elastic deformation in the fitted portion. That is, when as shown in FIG. 14 of the accompanying drawings which schematically shows a cross-sectional view of the fitted portion, an error of positional dimensions occurs between the center of the circulation path straight portions 5 and the center of the protruding portion 25 lying in the opening portion of the circulation path curved portion 6, there has been the undesirable possibility that the slider body 1 and the end cap 2 do not closely contact with each other and a gap or a level difference of unexpected magnitude is created even on the endless track of the balls.
Here, when the diameter of the circulation path is defined as xcfx86 and the diameter of the balls is defined as Da, the gap G between the balls located in the circulation path and the inner wall of the circulation path is represented by the following expression (1):
G=xcfx86xe2x88x92Daxe2x80x83xe2x80x83(1)
Further, assuming that A indicates the positional dimension from the center line of the slider body 1 to the center line of the circulation path straight portions 5 and B indicates the positional dimension from the center line of the end cap 2 to the center of the opening in the circulation path curved portion 6, the diameter of the circulation path substantially coincides with L0 in the fitted portion when as shown in FIG. 13, the positional dimensions coincide with each other (A=B), and assuming that the length of the portion in which the diameter of the circulation path changes to effect fitting is xcex94, the gap in the fitted portion, i.e., the gap between the balls and the inner wall of the circulation path, is represented by the following expression (2):
G=(xcfx862+xcex942)xc2xdxe2x88x92Daxe2x80x83xe2x80x83(2)
Further, when as shown in FIG. 14, the error of the positional dimensions is Axe2x88x92B, L1 and L2 are conceivable as the substantial diameters in the circulation path, but the diameters in question are great in absolute amount. In this case, L2 greater than L1 and therefore, when the extension of the portion in which the diameter of the circulation path created without the slider body and the end cap closely contacting with each other changes is defined as xcex4, the gap in question is represented by the following expression (3):
G={[xcfx86+(Axe2x88x92B)]2+(xcex94+xcex4)2}xc2xdxe2x88x92Daxe2x80x83xe2x80x83(3)
That is, the gap between the inner wall of the circulation path in the fitted portion and the balls increases in conformity with an increase in the dimensional difference between A and B and the resultant increase in xcex4.
The increase in the gap between the inner wall of the circulation path and the balls is an increase in the magnitude of the amount of play when the balls pass the fitted portion, and this causes the collision of the balls against the wall surface of the circulation path. This problem particularly remarkably arose outside the orbit of revolution of the balls, and as the result, it increased the noise created during the running of the linear guide device, i.e., when the slider body moved on the guide rail.
The present invention has as its object to provide a linear guide device which decreases the play of balls relative to the orbit of revolution thereof to thereby decrease the collision of the balls against the wall surface of a circulation path and suppress the noise during the running of the device.
In order to solve the above-noted problem, the present invention provides a linear guide device comprising a guide rail having in the outside thereof a first groove portion extending axially and supporting a plurality of rolling members for rolling therein, and a slider having a second groove portion opposed to the first grove portion and constituting a space in which the rolling members roll and a circulation path communicating with the space formed by the first and second groove portions and constituting an endless track for circulating the plurality of rolling members therein, and supported on the guide rail through the rolling members in the second groove portion and sliding on the guide rail by the plurality of rolling members rolling in the space, the slider being comprised of a slider body having a circulation path straight portion constituting the second groove portion and a part of the circulation path independently of the second groove portion, and two end caps mounted on the opposite end portions of the slider body and having circulation path curved portions constituting the endless track by being communicated with each other in the opposite end portions of the space formed by the first and second groove portions and the circulation path straight portion, characterized in that the end caps further have in the opening portion of the circulation path curved portions communicating with the circulation path straight portion a substantially cylindrical convex portion disposed so as to extend the circulation path curved portions toward the circulation path straight portion and divided into at least two, and the slider body has in the opening portion of the circulation path straight portion communicating with the circulation path curved portions a substantially cylindrical concave portion corresponding to the substantially cylindrical convex portion for the slider body and the end caps to constitute faucet-fitting.
According to the present invention, even when in the communicating portion of the circulation path straight portion and the circulation path curved portion, an error occurs to their positional dimensions, the divided cylindrical convex portion of the end caps faucet-fitted to the slider body is deformed when fitted and therefore, a gap in the lengthwise direction of the fitted portion which may pose a problem in the prior art is not created or it becomes possible to make the gap small. The substantially cylindrical convex portion increases its deformation potential by being divided, and it becomes possible to more improve the closely contacting property between the slider body and the end caps related to the endless track.
However, the closely contacting property of the faucet-fitted portion is improved by the deformation of the divided cylindrical convex portion, while on the other hand, there occurs a case where a level difference is created in the circulation path by the deformation and hinders the smooth rolling of the balls. So, in order to achieve the above object, in the linear guide device according to the present invention, in the cylindrical convex portion used as the faucet-fitted portion, the inner edge portion of the tip end portion thereof toward the circulation path may be formed with a taper for enlarging the opening diameter toward the tip end portion. This tapered portion may form a chamfered or curved surface.